Influence of interfacial depth on depth resolution during GDOES depth profiling analysis of thin alumina films

Factors controlling the depth resolution in radio frequency glow discharge optical emission spectroscopy (rf-GDOES) depth profiling analysis of thin films have been investigated using anodic alumina films of varying thicknesses with delta function marker layers of similar to2 nm width located at various depths from the oxide surface. In rf-GDOES depth profiling analysis, where a relatively large area of similar to4 mm in diameter is analysed, it was found that the depth resolution is determined mainly by the large-scale variation of sputtering rate across the crater. Despite the relatively large area analysed, the uniformity of sputtering rate across the crater was constant to within 1% under the optimum Ar pressure except for near-edge regions of similar to0.4 min width, where the sputtering rate was similar to6% higher than in the central crater region. Owing to this relatively minor non-uniformity of sputtering rate, the depth resolution degrades approximately linearly with depth. A depth resolution of similar to1.3 nm was realized to depths of similar to 25 mn, where the degradation of depth resolution due to the non-uniformity in sputtering rate is insignificant. The depth resolution is close to the ultimate depth resolution in sputter depth profiling, claimed to be 0.7-1.0 run, and arises from the minimal atomic mixing associated with film sputtering with Ar(+)ions of very low energy, similar to 50 eV, in rf-GDOES analysis. Copyright (C) 2001 John Wiley & Sons, Ltd.